"Once we get an idea about the location and the cause, we'll go with the bulldozers and try to level out some more areas and make sure it's safe before we bring the cadaver dogs in," said Cleo Doss of the San Jose Fire Department.

Fire officials said that the investigation could take up to a couple of weeks.

The building had been abandoned for about a decade, after KNTV left the premises in 2004, though up to 30 homeless people set up camp inside.

More than a dozen homeless people were apparently living inside the abandoned building at the time of Sunday’s fire.

Investigators told NBC Bay Area they suspect the fire was started by a person, because there were many homeless people inside at the time who had brought in their BBQ grills, propane tanks and motorcycles.

There was some speculation from homeless people on Monday that another transient may have been responsible for the fire. Ace McCoy told NBC Bay Area that one homeless person he knew may have had a grudge against others because he had been asked to leave after he had been stealing from other transients in the building.

But no official word on the cause has been released, and arson investigators did not immediately respond to McCoy's allegation. Firefighters could not immediately tell whether the fire was started on purpose or by accident. Firefighters also used the building - which KNTV occupied from 1955 to 2004 - for training purposes.

The City of San Jose is responsible for the publicly-owned building and was in the process of getting permits to tear it down and make way for a possible new Oakland A's stadium.